This invention relates to a process for mild hydrocracking hydrocarbon feeds. According to a specific aspect of the invention, mild hydrocracking is employed to produce hydrogenated catalytic cracker feeds from distillates. According to a further aspect of the invention, mild hydrocracking is employed in preparation of dewaxed lube oil base stocks.
Mild hydrocracking of petroleum and synthetic crude oil fractions in the presence of shape selective catalysts capable of selectively cracking n-paraffins and isoparaffins is well known. For example, U.S. Pat. No. Re. 28,398 (Chen et al.,), which is a reissue of U.S. Pat. No. 3,700,585, discloses the use of shape selective crystalline aluminosilicate zeolite ZSM-5 in catalytic dewaxing processes directed at removing high freezing point paraffins from jet fuel to lower the freezing point, improving the octane rating of naphtha fractions and lowering the pour point of lube oil base stocks. According to Chen et al. the shape selective cracking ability of crystalline aluminosilicate ZSM-5 permits selective cracking of n-paraffins and certain isoparaffins without substantial cracking of desirable feed components such that improved catalytic dewaxing products are obtained under both hydrotreating and hydrocracking conditions. Chen et al. also discloses the use of crystalline aluminosilicate zeolite ZSM-5 associated with hydrogenating metals such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, platinum or palladium, such metals being associated with the zeolite by exchange or impregnation.
An abstract of U.S. Pat. No. Re 30,529, which is a reissue of U.S. Pat. No. 4,100,056, discloses catalytic dewaxing of atmospheric and vacuum distillates in the presence of a catalyst containing mordenite in hydrogen form and a Group VI or VIII metal to obtain naphthenic lube oils of intermediate viscosity index and pour points ranging from -50.degree. to +20.degree. F.
An abstract of U.S. Pat. No. 4,222,855 discloses catalytic dewaxing of 450.degree.-1,050.degree. F. hydrocarbon fractions to produce high viscosity index lube oils employing a catalyst containing crystalline aluminosilicate zeolite ZSM-23 or ZSM-35, preferably in hydrogen form and associated with platinum, palladium or zinc. According to the abstract, the use of catalysts containing crystalline aluminosilicate zeolite ZSM-23 or ZSM-35 gives products of higher viscosity index and lower pour point than products obtained through the use of crystalline aluminosilicate zeolite ZSM-5.
U.S. Pat. No. 4,247,388 (Banta et al.) is directed to improving crystalline aluminosilicate zeolites such as ZSM-5 in terms of dewaxing performance by treatment to adjust alpha activity. According to the patentee, alpha-activity is adjusted by partial replacement of cationic sites of the crystalline aluminosilicate zeolite with basic cations such as sodium, by partial coking of the zeolite, by employing the zeolite in combination with an inert matrix material, by manipulating the silica to alumina ratio of the zeolite, or preferably, by steaming. Crystalline aluminosilicate zeolites adjusted in terms of alpha activity can be employed in association with exchanged or impregnated hydrogenating metals such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, platinum or palladium. A disclosure similar to that of Banta et al. is found in an abstract of British Pat. No. 2,027,742.
U.S. Pat. No. 4,251,348 and U.S. Pat. No. 4,282,085 (both O'Rear) are directed to processes similar to those described hereinabove wherein a low nitrogen content petroleum distillate fraction boiling from 180.degree.-1,200.degree. F. is contacted with crystalline aluminosilicate zeolite ZSM-5 or a similar crystalline aluminosilicate zeolite in a form substantially lacking in hydrogenation activity to form an effluent which then is fractionated into an upgraded product stream and a C.sub.3 -C.sub.4 olefin fraction. If desired, the crystalline aluminosilicate zeolite can be dispersed in a porous matrix having only insubstantial cracking activity. Suitable matrix materials include pumice, firebrick, diatomaceous earth, alumina, silica, zirconia, titania, amorphous silica-alumina mixtures, bentonite, kaolin, silica-magnesia, silica-zirconia or silica-titania. A similar disclosure is found in an abstract of Belgium Pat. No. 877,772.
U.S. Pat. No. 4,259,174 (Chen et al.) discloses catalytic dewaxing of hydrocarbon feeds to reduce pour point and produce high viscosity index distillate lube oil stocks in the presence of a synthetic offretite crystalline aluminosilicate zeolite catalyst which may contain exchanged or impregnated hydrogenating metals such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, platinum or palladium. The crystalline aluminosilicate zeolite may be dispersed within a matrix of alumina, silica, silica-alumina, etc. Column 5 line 67-Column 6 line 17. It is unclear whether the patentee contemplates use of the crystalline aluminosilicate zeolite in association with both hydrogenating metals and matrix materials.
An abstract of British Pat. No. 2,055,120 (Mobil) discloses a method for reclaiming or upgrading contaminated, dewaxed lube oil base stocks having a tendency to form a waxy haze during storage, comprising contacting the oil with hydrogen at 500.degree.-675.degree. F. and space velocity of 2-10 in the presence of a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least 12 and a constraint index of 1-12.
In preparation of lube oils from waxy hydrocarbon feeds, catalytic dewaxing processes such as described hereinabove often are combined with hydrotreating, hydrocracking and/or various solvent extraction steps to obtain products having desired properties. Typically, hydrocracking and/or solvent extraction steps are conducted prior to catalytic dewaxing to remove components such as metal-containing feed components, asphaltenes and polycyclic aromatics having properties that differ grossly from those desired. In particular, solvent extraction is conducted to remove polycyclic aromatic feed components and nitrogen-containing cyclic components, removal of the latter being particularly important in order to avoid poisoning of the catalyst in catalytic dewaxing. Hydrotreating under mild or severe conditions typically follows catalytic dewaxing operations and serves to improve such lube oil properties as stability and viscosity index.
As one example of a process for producing lube oils in which a catalytic dewaxing step is included as part of a multistep process, U.S. Pat. No. 4,259,170 (Graham et al.) discloses a process that includes a combination of catalytic dewaxing and solvent dewaxing steps. According to a more specific aspect of Graham et al., the process includes a solvent extraction step prior to the dewaxing steps. As a further example of a multistep process for preparation of lube oils, Chen et al., '174, discussed hereinabove, discloses a process comprising solvent extraction followed by catalytic dewaxing. Finally, U.S. Pat. No. 4,283,272 (Garwood et al.) discloses preparation of lube oils by a process that includes hydrocracking, catalytic dewaxing and hydrotreating steps. In each of these multistep processes, the catalytic dewaxing step employs a catalyst containing a crystalline aluminosilicate zeolite, and optionally, exchanged or impregnated hydrogenating metals.
In addition to mild hydrocracking to catalytically dewax waxy hydrocarbons, mild hydrocracking can be employed to produce catalytic cracking feeds from heavy, contaminant-containing hydrocarbons such as high sulfur content gas oils and hydrotreated residual fractions. As such, mild hydrocracking can add flexibility to the combination of hydroprocessing and catalytic cracking in that yields of hydrogenated distillates and gasoline can be adjusted on the basis of demand by employing mild hydrocracking of distillates to catalytic cracking feedstocks thereby ultimately increasing gasoline yields where desired, or by conducting conventional hydroprocessing operations when increased distillate yields are desired.
It would be desirable to improve mild hydrocracking processes such as catalytic dewaxing or catalytic cracker feed hydrocracking to render such processes suitable for use with a broader range of feed materials, e.g. high sulfur or nitrogen content feeds such as those derived from low quality petroleum crude oils and synthetic hydrocarbon sources such as shale oil, tar sands oils, coal liquids and biomass liquids.
It is an object of this invention to provide an improved mild hydrocracking process. A more specific object is to provide improved dewaxing mild hydrocracking and catalytic cracking feed mild hydrocracking processes applicable with respect to a broader range of feeds. A still more specific object of the invention is to provide a single step process for production of lube oil base stocks. Other objects of the invention will be apparent to persons skilled in the art from the following description and the appended claims.
We have now found that the objects of this invention can be attained by mild hydrocracking of hydrocarbon feeds in the presence of an improved catalyst composition comprising an active metallic component comprising at least one metal having hydrogenating activity and at least one oxygenated phosphorus component, and a support component comprising a non-zeolitic, porous refractory inorganic matrix component and a shape selective zeolitic cracking component. Advantageously, mild hydrocracking with such catalysts can be conducted at conditions severe enough to allow use of feeds containing high levels of contaminants without substantial destruction of desirable feed components. In catalytic dewaxing processes, not only are waxy feed components cracked according to the present invention, but also, contaminants such as sulfur, oxygen and nitrogen are removed. In fact, according to one aspect of the invention, lube oil stocks of desirably low pour point, high viscosity index and good stability are produced from waxy petroleum or synthetic crude oil feed materials, which may contain appreciable levels of contaminants such as sulfur, nitrogen and/or oxygen, by a single step process involving catalytic dewaxing in the presence of the aforesaid catalyst. In catalytic cracking feed mild hydrocracking, desirable results are attained in terms of both cracking and hydrogenation to remove contaminants such as sulfur or nitrogen.
In connection with the present invention, it is to be noted that hydrogen processing catalysts containing a hydrogenating component comprising a chromium component, a molybdenum component and at least one Group VIII metal component, and a porous refractory inorganic oxide component and a crystalline molecular sieve zeolite component are disclosed and claimed in copending, commonly assigned application Ser. No. 200,536 of Tait et al. filed Oct. 24, 1980. Such catalysts preferably are employed for hydrodenitrogenation and hydrocracking of high nitrogen feeds. Suitable zeolites according to such earlier application include shape selective crystalline molecular sieve zeolites among others. In copending, commonly assigned application Ser. No. 231,757 of Miller filed Feb. 5, 1981, improved hydrotreating catalysts comprising a hydrogenating component comprising a chromium component, at least one additional Group VIB metal component, at least one Group VIII metal component and at least one phosphorus component supported on a refractory inorganic oxide support are disclosed and claimed as are hydrotreating processes employing such catalysts. Particularly good results are attained in denitrogenation processes according to Miller.